PIV Applet

The CanoKey PIV applet implements the mandatory features of NIST SP 800-73-4 and a set of extensions. This page documents CanoKey-specific behavior and the commands exposed by the implementation. Refer to NIST SP 800-73-4 for the standard command and TLV definitions.

1. Application and Transport

1.1 AID

The PIV application identifier is:

A0 00 00 03 08 00 00 10 00 01 00

Select it with 00 A4 04 00 0B A000000308000010000100.

1.2 APDU Transport

CanoKey accepts short APDUs. Extended-length command APDUs are rejected with 6700.

When response data does not fit in one response, CanoKey returns 61xx. Use Get Response (INS = C0) to retrieve the remaining data.

1.3 Instructions

INS Name Definition
20 Verify NIST SP 800-73-4
24 Change Reference Data NIST SP 800-73-4
2C Reset Retry Counter NIST SP 800-73-4
47 Generate Asymmetric Key Pair NIST SP 800-73-4
87 General Authenticate NIST SP 800-73-4
A4 Select ISO 7816-4
C0 Get Response ISO 7816-4
CB Get Data NIST SP 800-73-4
DB Put Data NIST SP 800-73-4
EE Algorithm Extension CanoKey extension
F7 Get Metadata Yubico-compatible extension
F8 Get Serial Yubico-compatible extension
FB Reset Yubico-compatible extension
FD Get Version Yubico-compatible extension
FE Import Asymmetric Key Yubico-compatible extension
FF Set Management Key Yubico-compatible extension

2. Algorithms

2.1 Algorithm IDs

The standard algorithm IDs are fixed. IDs for the extended algorithms are configurable and must be read from the device when interoperability depends on their values.

Algorithm Default ID Availability
RSA 2048 07 All supported firmware versions
NIST P-256 11 All supported firmware versions
NIST P-384 14 All supported firmware versions
RSA 3072 05 3.0.0+
RSA 4096 16 3.0.0+
Ed25519 E0 3.0.0+
X25519 E1 3.0.0+
secp256k1 53 3.0.0+
SM2 54 3.0.0+

Firmware version 3.0.0 accepts only 32-byte input for Ed25519 signing and only internally generated X25519 keys. Firmware version 3.0.2 and later remove these restrictions.

2.2 Algorithm Extension Command

The Algorithm Extension command reads or writes the seven-byte extended-algorithm configuration record.

Operation APDU header Authentication Data
Read 00 EE 01 00 None Empty
Write 00 EE 02 00 Management key Seven-byte record

The record fields are ordered as follows:

Offset Field Default
0 Extended algorithms enabled 01
1 Ed25519 ID E0
2 RSA 3072 ID 05
3 RSA 4096 ID 16
4 X25519 ID E1
5 secp256k1 ID 53
6 SM2 ID 54

The enable field must be 00 or 01. Algorithm IDs can use any byte value and may overlap. A successful write takes effect immediately.

3. Key Slots and Policies

Slot Purpose Default PIN policy Default touch policy
9A PIV Authentication Once Never
9C Digital Signature Once Never
9D Key Management Once Never
9E Card Authentication Never Never
82-83 Retired Key Management Once Never

Firmware version 2.0.0 and later support Retired Key Management slots 82 and 83.

PIN policies use Never, Once, and Always. Touch policies use Never, Always, and Cached; the cached interval is 15 seconds. Touch requirements apply only over USB and are not enforced over NFC.

4. Data Objects

Get Data and Put Data use the standard 5C tag list and 53 data container defined by NIST SP 800-73-4. All writable objects require management-key authentication.

Tag Data object Capacity
7E Discovery Object Synthesized
5FC101 Card Authentication Certificate 3000 bytes
5FC102 Cardholder Unique Identifier 2916 bytes
5FC105 PIV Authentication Certificate 3000 bytes
5FC107 Card Capability Container 287 bytes
5FC109 Printed Information 245 bytes
5FC10A Digital Signature Certificate 3000 bytes
5FC10B Key Management Certificate 3000 bytes
5FC10D-5FC10E Retired Key Management Certificates 3000 bytes each
Certificate capacities are 3000 bytes on firmware version 1.6 and later and 1000 bytes on firmware version 1.5 and earlier.

5. Other Extension Commands

5.1 Get Metadata

Use 00 F7 00 <reference> with no data. The reference can be PIN (80), PUK (81), management key (9B), or a supported asymmetric-key slot. The response follows the Yubico PIV metadata TLV format and reports values such as algorithm, policies, origin, public key, default status, and retry counters where applicable.

5.2 Get Serial and Version

  • 00 F8 00 00 returns the four-byte device serial number.
  • 00 FD 00 00 returns the three-byte PIV applet version.

5.3 Import Asymmetric Key

Use INS = FE, with the algorithm ID in P1 and the destination slot in P2. Management-key authentication is required. The imported key format follows the Yubico PIV TLV format.

5.4 Reset

Use 00 FB 00 00 with no data. Reset is accepted only when both PIN and PUK are blocked. It restores PIV user data and defaults.